1. Technical Field
The present disclosure relates to an apparatus for detecting a defect of an electric power system, which is connected to the electric power system.
2. Description of the Related Art
An apparatus for detecting a defect of an electric power system is an electric power device which is connected to the electric power system to detect a defect current when the defect current such as an overcurrent or a short circuit current is generated at the electric power system. The apparatus for detecting a defect of an electric power system trips a circuit breaker (that is, automatically breaks a circuit) or limits a current (breaks a circuit to limit a conducting current) when a defect current is detected.
FIG. 1 is a diagram illustrating a conventional apparatus for detecting a defect of an electric power system. Hereinafter, an operation process of the conventional apparatus 10 for detecting a defect of an electric power system will be described with reference to FIG. 1. The conventional apparatus 10 for detecting a defect of an electric power system may determine whether a defect of an electric power system occurs or not based on a magnitude of a line current and an increase ratio thereof.
Firstly, a detector 11 detects a magnitude of a line current, and an amplifier 12 amplifies the detected magnitude of the line current. Thereafter, a comparator 13 compares the amplified magnitude of the line current with a first set value Ref1 and may output a first output signal when the amplified magnitude of the line current is equal to or greater than the first set value Ref1.
Meanwhile, a differentiator 14 calculates an increase ratio of the line current, and an amplifier 15 amplifies the calculated increase ratio of the line current. Thereafter, a comparator 16 compares the amplified increase ratio of the line current with a second set value Ref2 and may output a second output signal when the amplified increase ratio of the line current is equal to or greater than the second set value Ref2. Afterward, a determination unit 17 may determine whether the electric power system is failed or not on the basis of the first output signal and the second output signal.
However, there is a problem in that the conventional apparatus 10 for detecting a defect of an electric power system could only determine whether the electric power system is failed or not and could not determine whether noise occurs or not.
That is, the conventional apparatus 10 for detecting a defect of an electric power system determines whether noise occurs or not after detecting whether the electric power system is failed or not, and then stops an operation when the noise occurs. Consequently, there is a problem in that the conventional apparatus 10 for detecting a defect of an electric power system could not detect whether the electric power system is failed during the operation stoppage due to an input of noise. Also, there is a problem in that the conventional apparatus 10 for detecting a defect of an electric power system is sensitive to noise to perform an incorrect operation owing to the noise.